More from WebMD

April 9, 2012 -- Women who are obese and/or have diabetes or high blood pressure during pregnancy may be about 60% more likely to have babies with autism, a new study suggests. While the new research points to an association between mom's health during pregnancy and autism, it's important to note that "we can't really draw causal links," says researcher Paula Krakowiak. She is a PhD candidate in epidemiology at the University of California, Davis.

But "it is already known that any of these conditions have downstream risks in terms of pregnancy complications and delivery complications. The take-home message would be that any modifiable changes that one can make in their lifestyle or diet can benefit these conditions and potentially benefit the baby."

Parallel Rise in Obesity, Diabetes, Autism Cited as Reason for Study

The study included more than 1,000 children aged 2 to 5. Of these, 517 had autism and 172 had other developmental disorders. Women who were obese and/or had diabetes or high blood pressure during pregnancy were about 60% more likely to have a child with autism and more than twice as likely to have a child with another type of developmental delay. "Obesity was the most striking risk in the autism group," Krakowiak tells WebMD.

According to the study, 34% of U.S. women of childbearing age are obese and 8.7% have diabetes. The most recent statistics from the CDC show that 1 in every 88 U.S. children -- and 1 in 54 boys -- has autism. Autism is up 78% since 2002. The parallel rise in these conditions is what prompted Krakowiak and her colleagues to look at this issue. Their findings will appear in the May issue of Pediatrics.

Prenatal Care Improves Health of Mother, Baby

"Given what we are learning about immune and metabolic problems in [autism], it is not surprising that the mother's condition could affect the infant," says Martha Herbert, MD, PhD, in an email. She is a pediatric neurologist at Massachusetts General Hospital and Harvard Medical School in Boston and the author of The Autism Revolution: Whole-Body Strategies for Making Life All It Can Be. "This is not only a public health problem, but raises the possibility that more aggressive lifestyle modification could reduce the risk for having [children with] autism or developmental delay in this group of mothers."

Alycia Halladay, PhD, agrees: "This study adds to the evidence that maternal health and prenatal factors may play a role in risk for autism." She is the director of research for environmental sciences at Autism Speaks, an advocacy group.

One theory involves a common thread of insulin resistance. If a person becomes resistant to the effects of the hormone insulin, the pancreas secretes more to control blood sugar levels. If it cannot produce enough insulin, blood sugar rises, and diabetes may develop.

"If the inability to regulate glucose is contributing to these effects, monitoring glucose, modifying your diet, and taking insulin could be three things to do not just in regard to lowering autism risk, but also to improve your health and that of the baby," Halladay says.

Other prenatal factors have been linked to autism risk. These include prenatal infection, immune system issues, and delivery complications. "Improving maternal health during pregnancy leads to the best outcomes for mothers and children," she says.

Not Enough Evidence Yet?

Andrew Adesman, MD, says it is too early to connect the dots between autism and maternal health during pregnancy. He is the chief of developmental and behavioral pediatrics at the Steven & Alexandra Cohen Children's Medical Center in New Hyde Park, N.Y. "This study suggests that health conditions in pregnant women may pose some increased risks for developmental problems in children," he says.

"[But] we must resist temptation to look at the rising rates of these conditions and presume that there is a solid causality," Adesman says. "We don't know that the increase in autism is due to increases in obesity, hypertension, and diabetes."

That said, "pregnant women, for a multitude of reasons, are best advised to optimize their health, including weight, blood pressure, and glucose control."